The invention relates to an apparatus for the continuous or semi-continuous casting of molten aluminium to form an ingot in the mould of a casting machine, the apparatus comprising a launder, a casting mould and feed means which are coupled to the launder and extend into the casting mould. The invention also relates to a method for the continuous or semi-continuous casting of molten aluminium to form ingots from a launder by using feed means which are coupled to the feed trough and extend into a casting mould.
It should be noted that where the present patent application refers to ingots, this term is also intended to include billets (which have an essentially round cross sectional area) or other forms of castings.
An apparatus for casting aluminium ingots which is in widely used on an industrial scale uses two metal levels and comprises a launder or a transfer ladle positioned at a higher level than the casting mould or series of casting moulds beneath it. Apparatus of this type include, without any restriction being made, apparatus for the direct chill casting (DC) process and the electromagnetic casting (EMC) process. Molten aluminium is transferred from a casting furnace, via the launder into the casting mould by means of feed means, such as a spout, an immersion pipe or a casting nozzle, said feed means being coupled to the launder and often forming an exit port in the bottom or base of the launder. The casting nozzle exits below the meniscus of the molten aluminium into the casting mould. The exit or outlet opening of the casting nozzle is generally situated approximately 20 to 60 mm below said meniscus. To enable the flow of the aluminium out of the casting nozzle into the casting mould to be controlled to some extent in terms of direction and velocity, and therefore also to allow the ultimate macro-segregation profile in the cast ingot to be controlled, it is customary for a bag made from a glass-fibre material to be situated beneath the outlet opening.
A drawback of using a such a glass-fibre bag is that an individual cast is generally difficult to reproduce. Another drawback is that oxides may adhere to the glass-fibre material during casting, and at irregular intervals become detached from this material, thus having an adverse effect on the quality of the ingot. Another drawback is that in the start-up phase of a casting operation there may be an accumulation of large quantities of oxides in the glass fibre bag, which oxides then, during casting, may enter into the cast ingot and consequently have an adverse effect on the quality of the ingot.
An object of the invention is to provide an improved apparatus which does not have the above mentioned drawbacks, or at least has these drawbacks to a much lesser extent.
Another object of the invention is to provide a method for casting aluminium ingots which does not have the above mentioned drawbacks or at least has these drawbacks to a much lesser extent.